You can only use each of the following effects of "Avendread Savior" once per turn
Its an ability doubler for abilities that trigger from casting spells, which includes prowess, magecraft, and anything else that says when you cast an instant/sorcery. I like that this plays an aggressive game plan but still feels very much Izzet, leaning into prowess and spellcasting to get the game over with
They could reprint these cards by creating similar but worse cards by slightly changing their mana cost, another stat, or type, but thats not the issue
In some rare cases, you might want to wait until the last possible moment to use your Kill Shot, even though it means allowing the creature to deal damage first
Normally, your Vanilla will be in Defense Position, so converting it into Imduk provides an attack and/or destroy, which is nice